1. Field of the Invention
The invention relates generally to apparatus for controlling a press brake, more specifically the invention relates to automated apparatus for sequentially positioning a gauge and a ram of a press brake during the operation of causing a series of bends in a workpiece.
2. Description of the Prior Art
In recent years there has been substantial development in the area of automation of press brakes and other metal forming machinery. U.S. Pat. No. 3,618,349 issued to Gerald V. Roch on Nov. 9, 1971 discloses a relatively early application of automation in this area, and relates to a gauging system which includes the automatic programmed control of gauges on a press brake. U.S. Pat. No. 3,874,205, a patent issued to Gerald V. Roch and Edward H. Sonn on Apr. 1, 1973, is another patent in the area of press brake automation. This patent discloses a pre-programmable system and incorporates variable ram closing and return stroke lengths.
Recently microprocessors have been incorporated in more sophisticated automatic press brake control. U.S. Pat. No. 4,074,350 issued to Gerald V. Roch and James P. Wiles on Feb. 4, 1978 discloses a softwire control which includes a microprocesser to execute operating instructions according to a program stored in a program memory. U.S. Pat. No. 4,115,859 to Brisk et al. (issued Sept. 19, 1978) and British Pat. No. 1,549,676 to Arthur et al. (published Aug. 1, 1979) are two additional patents which disclose automated press brake controls incorporating microprocessors.
One complex aspect in the ram control of a press brake is the calculation or determination of the ram drive commands in order to reach the desired angle of bend in the workpiece. A number of variables affect the ultimate angle which is obtained; such as the thickness or kind of material which is being bent, the extent of the angle of bend which is to be caused, the size of the die opening and the calibration between the ram and the die.
Particularly, the "springback" of the metal workpiece is extremely difficult to predict. "Springback" is the tendency of the work material to spring back towards its original position after the pressure of the ram has been released. The extent to which material may spring back is subject to a number of factors and is not readily predetermined. Even with the same material, having the same characteristics within commercially accepted tolerances, the extent of springback may vary up to one degree.
Control apparatus of the prior art either provides for the specific positioning to be manually inputted, or provides for a means of calculating or estimating the positioning that would cause the desired angle after certain variables which affect that angle have been inputted. The prior art does not provide for interactive or sequential correction for workpiece springback in the operation of a press brake.
Optical digitizers have been used in a variety of fields. Such digitizers have a capability of converting optical reception into digital data. Optical digitizers have been used for purposes of monitoring and surveillance; inspection and precision measurement; part sorting and selection; medical analysis; and various types of automated manufacturing. They have not been used in the field of automated control of press brakes.